In a semiconductor device disclosed in JP 3525832, a front-surface electrode and a back-surface electrode are provided on a front surface and a back surface of a plate-shaped semiconductor element, respectively, and heatsinks made of metal such as copper (Cu) are placed on both surfaces of the semiconductor element so that the semiconductor element can be cooled from both surfaces. The electrodes are electrically and thermally connected to the heatsinks through a joint member such as solder.
However, in such a semiconductor device as disclosed in JP 3525832, there is a concern that the solder may be cracked or detached by thermal stress applied between the heatsink (e.g., made of copper) and the semiconductor element (e.g., made of silicon) due to a difference in coefficient of thermal expansion between the heatsink and the semiconductor element. In addition, since compressive stress is applied from the heatsink through solder to the semiconductor element during a high-temperature process such as a reflow soldering, additional processing, such as thinning of the semiconductor element, is required to reduce the stress applied to the semiconductor element.
JP 3809550 discloses another semiconductor device. According to the semiconductor device disclosed in JP 3809550, multiple semiconductor elements are arranged in parallel in a package, and front-surface and back-surface electrodes of each semiconductor element are in surface contact with top and bottom heatsinks of the package under pressure to the heatsinks from outside. In such an approach, the problem caused by the use of solder may be prevented.
The semiconductor device disclosed in JP 3809550 includes not only a tube made of an electrically insulating ceramic material placed between the heatsinks to increase a creepage distance between the front-surface and back-surface electrodes of the semiconductor element but also a supporting member placed between adjacent semiconductor elements. Therefore, a large number of parts and manufacturing processes are required.